JP6956038B2 - Carrier for electrically heated catalyst - Google Patents

Description

The present invention relates to an electrically heated catalyst carrier. In particular, in an electrically heated catalyst carrier including a honeycomb structure and a pair of metal electrode portions arranged so as to face each other with the center of the honeycomb structure interposed therebetween, the coefficient of thermal expansion between the honeycomb structure and the metal electrode portion. The present invention relates to an electrically heated catalyst carrier that can effectively suppress damage to the honeycomb structure due to the difference between the two.

Conventionally, a honeycomb structure made of cordierite or silicon carbide with a catalyst supported has been used for treating harmful substances in exhaust gas discharged from an automobile engine (see, for example, Patent Document 1). Such a honeycomb structure generally has a columnar honeycomb structure having a partition wall that serves as a flow path for exhaust gas and partitions a plurality of cells extending from one bottom surface to the other bottom surface.

When treating exhaust gas with a catalyst supported on a honeycomb structure, it is necessary to raise the temperature of the catalyst to a predetermined temperature. However, when the engine is started, the catalyst temperature is low, so that the exhaust gas is not sufficiently purified. rice field. Therefore, by arranging electrodes on the honeycomb structure made of conductive ceramics and heating the honeycomb structure itself by energization, the catalyst supported on the honeycomb structure is raised to the active temperature before or when the engine is started. A system called an electric heating catalyst (EHC) has been developed.

In order to pass an electric current through the EHC, it is necessary to make an electrical connection with the external wiring, but during energization heating, heat due to the difference in linear expansion coefficient between the metal material that constitutes the surface electrodes and wiring and the ceramic material that constitutes the carrier. Distortion occurs. Therefore, a member having a stress buffering function is required so as not to apply thermal strain due to the difference in linear expansion coefficient to the EHC carrier.

In Patent Document 1, as one of the measures, wiring for supplying electric power from the outside to a pair of surface electrodes extending in the axial direction of the carrier surface is formed into a comb-like shape, and a plurality of wires are sprayed onto the same comb-tooth. It is disclosed that thermal strain (thermal stress) based on the difference in linear expansion coefficient between a wiring made of metal and a carrier made of ceramics is relaxed by fixing points and providing a bent portion between them.

Japanese Patent No. 5761161

However, if a plurality of points are fixed on the same comb tooth, the expansion differs depending on each point due to the heat generation distribution or the like, and stress is applied to the fixed point (contact point), which may cause the contact point to break. It is also considered to provide a bent portion to relieve the stress, but the torsional stress cannot be dealt with and the contacts may be broken.

Further, a method of fixing the same electrode at only one point has been raised, but it is considered that the range of current that can be handled is narrowed because the number of contacts is reduced.

The present invention has been made in consideration of the above problems, and is for an electrically heated catalyst having a honeycomb structure and a pair of metal electrode portions arranged so as to face each other with the center of the honeycomb structure interposed therebetween. An object of the present invention is to provide a carrier for an electrically heated catalyst capable of effectively suppressing damage to the honeycomb structure due to a difference in thermal expansion coefficient between the honeycomb structure and the metal electrode portion.

As a result of diligent studies, the present inventor has provided a plurality of tongue pieces protruding from the main body portion of the metal electrode portion, and brought the tongue pieces into contact with the honeycomb structure to obtain a linear expansion coefficient between the metal electrode portion and the honeycomb structure. It has been found that the honeycomb structure can be prevented from being subjected to excessive stress due to thermal strain (thermal stress) based on the difference, and the above-mentioned problems can be solved. That is, the present invention is specified as follows.
(1) Honeycomb structure and
An electrically heated catalyst carrier including a pair of metal electrode portions arranged so as to face each other with the center of the honeycomb structure interposed therebetween.
One or both of the pair of metal electrode portions includes a plate-shaped main body portion and a plurality of tongue pieces protruding from the main body portion, and a part of the tongue pieces comes into contact with the honeycomb structure. A carrier for an electrically heated catalyst, which is characterized by being present.
(2) The shortest length A from the starting point of the tongue piece protruding from the main body portion to the portion where the tongue piece most protrudes, and the direction orthogonal to the direction of protrusion from the main body portion on the surface of the tongue piece. The carrier for an electrically heated catalyst according to (1), wherein the minimum value B of the width of the above satisfies the relationship of 1 ≦ A / B ≦ 10.
(3) The tongue piece has a neck and a head having a width wider than the width of the neck, and the length L1 of the neck and the length L2 of the head are 1 ≦ L1 / L2 ≦ 10. The carrier for an electrically heated catalyst according to (1) or (2), which satisfies the relationship of.
(4) The carrier for an electrically heated catalyst according to any one of (1) to (3), wherein the tongue piece has two or more bent portions.
(5) The honeycomb structure is provided with a pair of electrode layers on its side surface, and the pair of electrode layers are arranged so as to face each other with the center of the honeycomb structure interposed therebetween. The carrier for an electroheating catalyst described in Honeycomb.
(6) The carrier for an electrically heated catalyst according to any one of (1) to (5), wherein the metal electrode portion is an iron alloy, a nickel alloy, or a cobalt alloy.
(7) The carrier for an electrically heated catalyst according to any one of (1) to (6), wherein the main body portion has a plurality of holes.

According to the present invention, in an electrically heated catalyst carrier including a honeycomb structure and a pair of metal electrode portions arranged so as to face each other with the center of the honeycomb structure interposed therebetween, the honeycomb structure and the metal electrode portion Damage to the honeycomb structure due to the difference in the coefficient of thermal expansion can be effectively suppressed.

It is a figure which shows an example of the honeycomb structure in this invention. It is sectional drawing of the honeycomb structure in one Embodiment of this invention. It is a figure which shows the central angle of the electrode layer in one Embodiment of this invention. It is a figure which shows the arrangement of the metal electrode part in one Embodiment of this invention. It is a perspective view which shows the metal electrode part 1 by one Embodiment of this invention. It is a perspective view which shows the metal electrode part 1A by another embodiment of this invention. It is a perspective view which shows the metal electrode part 1B which concerns on still another Embodiment of this invention. It is a perspective view which shows the metal electrode part 1C which concerns on still another Embodiment of this invention. (A), (b), (c) and (d) are diagrams showing the planar morphology of the tongue pieces 7A, 7B, 7C and 7D, respectively. (A), (b) and (c) are diagrams showing the planar morphology of the tongue pieces 7E, 7F and 7G, respectively. It is a figure which shows the shape of the tongue piece. It is a figure which shows the bent part of the tongue piece.

Hereinafter, embodiments of the electrically heated catalytic carrier of the present invention will be described with reference to the drawings, but the present invention is not construed as being limited thereto, and is not deviated from the scope of the present invention. In, various changes, modifications and improvements can be made based on the knowledge of those skilled in the art.

(1. Honeycomb structure)
FIG. 1 shows an example of a honeycomb structure in the present invention. The honeycomb structure 10 includes, for example, a porous partition wall 11 that serves as a flow path for the fluid and partitions a plurality of cells 12 extending from the inflow end face which is the end face on the inflow side of the fluid to the outflow end face which is the end face on the outflow side of the fluid. It has an outer peripheral wall located at the outermost periphery. The number, arrangement, shape, etc. of the cells 12 and the thickness of the partition wall 11 are not limited, and can be appropriately designed as needed.

The material of the honeycomb structure 10 is not particularly limited as long as it has conductivity, and metal, ceramics, or the like can be used. In particular, from the viewpoint of achieving both heat resistance and conductivity, the material of the honeycomb structure 10 is preferably a silicon-silicon carbide composite material or a material containing silicon carbide as a main component, and the silicon-silicon carbide composite material or carbonized material is preferable. It is more preferably silicon. In order to lower the electrical resistivity of the honeycomb structure, tantalum silicide (TaSi _2), it can be blended chromium silicide (CrSi _2). The fact that the honeycomb structure 10 contains a silicon-silicon carbide composite as a main component means that the honeycomb structure 10 contains a silicon-silicon carbide composite (total mass) in an amount of 90% by mass or more of the entire honeycomb structure. Means that. Here, the silicon-silicon carbide composite material contains silicon carbide particles as an aggregate and silicon as a binder for binding the silicon carbide particles, and a plurality of silicon carbide particles are formed between the silicon carbide particles. It is preferably bonded by silicon so as to form pores. Further, the fact that the honeycomb structure 10 contains silicon carbide as a main component means that the honeycomb structure 10 contains silicon carbide (total mass) in an amount of 90% by mass or more of the entire honeycomb structure.

The electrical resistivity of the honeycomb structure 10 may be appropriately set according to the applied voltage, and is not particularly limited, but may be, for example, 0.001 to 200 Ω · cm. For high voltages of 64 V or higher, it can be 2 to 200 Ω · cm, typically 5 to 100 Ω · cm. Further, for a low voltage of less than 64 V, it can be 0.001 to 2 Ω · cm, typically 0.001 to 1 Ω · cm, and more typically 0.01 to 1 Ω. -Can be cm.

The porosity of the partition wall 11 of the honeycomb structure 10 is preferably 35 to 60%, more preferably 35 to 45%. If the porosity is less than 35%, the deformation at the time of firing may be large. If the porosity exceeds 60%, the strength of the honeycomb structure may decrease. Porosity is a value measured by a mercury porosimeter.

The average pore diameter of the partition wall 11 of the honeycomb structure 10 is preferably 2 to 15 μm, more preferably 4 to 8 μm. If the average pore diameter is smaller than 2 μm, the electrical resistivity may become too large. If the average pore diameter is larger than 15 μm, the electrical resistivity may become too small. The average pore diameter is a value measured by a mercury porosimeter.

The shape of the cell 12 in the cross section orthogonal to the flow path direction of the cell 12 is not limited, but is preferably a quadrangle, a hexagon, an octagon, or a combination thereof. Of these, squares and hexagons are preferred. By making the cell shape in this way, the pressure loss when the exhaust gas is passed through the honeycomb structure 100 is reduced, and the purification performance of the catalyst is excellent.

The outer shape of the honeycomb structure 10 is not particularly limited as long as it is columnar. It can have a columnar shape (octagonal shape, etc.). ^{Further, the size of the honeycomb structure 10 is preferably 2000 to 20000 mm 2} and preferably 4000 to 10000 mm ² from the viewpoint of enhancing heat resistance (preventing cracks entering the circumferential direction of the outer peripheral side wall). Is more preferable. Further, the axial length of the honeycomb structure 10 is preferably 50 to 200 mm, preferably 75 to 150 mm, from the viewpoint of enhancing heat resistance (preventing cracks entering parallel to the central axial direction on the outer peripheral side wall). Is more preferable.

Further, by supporting the catalyst on the honeycomb structure 10, the honeycomb structure 10 can be used as a catalyst carrier.

The honeycomb structure can be produced according to the method for producing a honeycomb structure in a known method for producing a honeycomb structure. For example, first, a metal silicon powder (metal silicon), a binder, a surfactant, a pore-forming material, water, or the like is added to silicon carbide powder (silicon carbide) to prepare a molding raw material. It is preferable that the mass of the metallic silicon is 10 to 40% by mass with respect to the total of the mass of the silicon carbide powder and the mass of the metallic silicon. The average particle size of the silicon carbide particles in the silicon carbide powder is preferably 3 to 50 μm, more preferably 3 to 40 μm. The average particle size of the metallic silicon particles in the metallic silicon powder is preferably 2 to 35 μm. The average particle size of the silicon carbide particles and the metal silicon particles refers to the arithmetic mean diameter based on the volume when the frequency distribution of the particle size is measured by the laser diffraction method. The silicon carbide particles are fine particles of silicon carbide constituting the silicon carbide powder, and the metallic silicon particles are fine particles of metallic silicon constituting the metallic silicon powder. This is a blending of molding raw materials when the material of the honeycomb structure is silicon-silicon carbide-based composite material, and when the material of the honeycomb structure is silicon carbide, metallic silicon is not added.

Examples of the binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol and the like. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The binder content is preferably 2.0 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass.

The water content is preferably 20 to 60 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass.

As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type, or may be used in combination of 2 or more type. The content of the surfactant is preferably 0.1 to 2.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon powder is 100 parts by mass.

The pore-forming material is not particularly limited as long as it becomes pores after firing, and examples thereof include graphite, starch, foamed resin, water-absorbent resin, and silica gel. The content of the pore-forming material is preferably 0.5 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metallic silicon powder is 100 parts by mass. The average particle size of the pore-forming material is preferably 10 to 30 μm. If it is smaller than 10 μm, pores may not be sufficiently formed. If it is larger than 30 μm, it may clog the base during molding. The average particle size of the pore-forming material refers to the arithmetic mean diameter based on the volume when the frequency distribution of the particle size is measured by the laser diffraction method. When the pore-forming material is a water-absorbent resin, the average particle size of the pore-forming material is the average particle size after water absorption.

Next, the obtained molding raw materials are kneaded to form a clay, and then the clay is extruded to produce a honeycomb structure. In extrusion molding, a mouthpiece having a desired overall shape, cell shape, partition wall thickness, cell density and the like can be used. Next, it is preferable to dry the obtained honeycomb structure. If the length in the central axis direction of the honeycomb structure is not the desired length, both bottom portions of the honeycomb structure can be cut to obtain the desired length.

Next, the dried honeycomb structure is fired to prepare a honeycomb structure. Prior to firing, it is preferable to perform temporary firing in order to remove binders and the like. The calcination is preferably carried out in an atmospheric atmosphere at 400 to 500 ° C. for 0.5 to 20 hours. The method of tentative firing and firing is not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like. The firing conditions are preferably 1400 to 1500 ° C. for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. Further, after firing, it is preferable to carry out an oxygenation treatment at 1200 to 1350 ° C. for 1 to 10 hours in order to improve durability.

(2. Electrode layer)
As shown in FIGS. 1 and 2, in the honeycomb structure 10 of the present embodiment, a pair of electrode layers 101a and 101b are arranged on the outer peripheral wall thereof, and each of the electrode layers 101a and 101b is a honeycomb structure 10. It is formed in a band shape extending in the extending direction of the cell 12. Further, in the cross section of the honeycomb structure 10 orthogonal to the extending direction of the cell 12, the pair of electrode layers 101a and 101b are arranged so as to face each other with the center of the honeycomb structure 10 interposed therebetween. Although the pair of electrode layers 101a and 101b are not essential in the present invention, the honeycomb structure 10 can suppress the bias of the current flowing in the honeycomb structure 10 when a voltage is applied, and the honeycomb structure 10 can suppress the bias of the current flowing in the honeycomb structure 10. It is preferable because the bias of the temperature distribution in the structure 10 can be suppressed.

The electrode layers 101a and 101b are made of a conductive material. The electrode layers 101a and 101b preferably contain silicon carbide particles and silicon as main components, and are more preferably formed from silicon carbide particles and silicon as raw materials, except for impurities normally contained. Here, "mainly composed of silicon carbide particles and silicon" means that the total mass of the silicon carbide particles and silicon is 90% by mass or more of the mass of the entire electrode layer. As described above, since the electrode layers 101a and 101b contain silicon carbide particles and silicon as main components, the components of the electrode layers 101a and 101b and the components of the honeycomb structure 10 are the same or similar components (material of the honeycomb structure). Is silicon carbide). Therefore, the coefficients of thermal expansion of the electrode layers 101a and 101b and the honeycomb structure are the same or close to each other. Further, since the materials are the same or similar, the bonding strength between the electrode layers 101a and 101b and the honeycomb structure 10 is also increased. Therefore, even if thermal stress is applied to the honeycomb structure, it is possible to prevent the electrode layers 101a and 101b from being peeled off from the honeycomb structure 10 and the joint portion between the electrode layers 101a and 101b and the honeycomb structure 10 from being damaged. be able to.

Further, it is preferable that the central angles α of the electrode layers 101a and 101b are 60 to 120 ° in the cross section orthogonal to the extending direction of the cell 12. The central angle α of one of the electrode layers 101a and 101b is preferably 0.8 to 1.2 times as large as the central angle α of the other electrode layers 101a and 101b, 1.0. It is more preferable that the size is doubled (same size). As a result, when a voltage is applied between the pair of electrode layers 101a and 101b, it is possible to suppress the bias of the current flowing through each of the outer peripheral region and the central region of the honeycomb structure. Then, it is possible to suppress the bias of heat generation in each of the outer peripheral region and the central region of the honeycomb structure.
Here, the central angle α means an angle formed by a straight line connecting both ends of the electrode layers 101a and 101b and the center O of the honeycomb structure in a cross section orthogonal to the extending direction of the cell 12 (see FIG. 3). In FIG. 3, the central angles α of the pair of electrode layers 101a and 101b have the same size.

In the honeycomb structure 10 of the present embodiment, the electrical resistivity of the electrode layers 101a and 101b is preferably lower than the electrical resistivity of the outer peripheral wall of the honeycomb structure 10. Further, the electrical resistivity of the electrode layers 101a and 101b is more preferably 0.1 to 10%, particularly preferably 0.5 to 5%, of the electrical resistivity of the outer peripheral wall of the honeycomb structure 10. preferable. If it is lower than 0.1%, when a voltage is applied to the electrode layers 101a and 101b, the amount of current flowing through the electrode layers 101a and 101b to the "end of the metal electrode portion" increases, and the honeycomb structure 10 has a large amount of current. The flowing current may be biased. Then, it may be difficult for the honeycomb structure 10 to generate heat uniformly. If it is higher than 10%, when a voltage is applied to the electrode layers 101a and 101b, the amount of the current spreading in the electrode layers 101a and 101b becomes small, and the current flowing through the honeycomb structure 10 may be easily biased. Then, it may be difficult for the honeycomb structure 10 to generate heat uniformly.

The thickness of the electrode layers 101a and 101b is preferably 0.01 to 5 mm, more preferably 0.01 to 3 mm. By setting it in such a range, it is possible to contribute to uniform heat generation of the honeycomb structure. If the thickness of the electrode layers 101a and 101b is thinner than 0.01 mm, the electrical resistivity may be high and uniform heat generation may not be possible. If the thickness of the electrode layers 101a and 101b is thicker than 5 mm, the electrode layers 101a and 101b may be damaged during canning.

As shown in FIG. 1, in the honeycomb structure 100 of the present embodiment, each of the electrode layers 101a and 101b extends in the extending direction of the cell 12 of the honeycomb structure 10 and "between both ends (between both end faces)". It is formed in the shape of a "honeycomb" band. As described above, in the honeycomb structure 100 of the present embodiment, the pair of electrode layers 101a and 101b are arranged so as to extend between both ends of the honeycomb structure 10. Thereby, when a voltage is applied between the pair of electrode layers 101a and 101b, the bias of the current in the axial direction of the honeycomb structure (that is, the direction in which the cell 12 extends) can be suppressed more effectively. Here, when it is said that "the electrode layers 101a and 101b are formed (arranged) so as to extend between both ends of the honeycomb structure 10", it means the following. That is, one end of the electrode layers 101a and 101b is in contact with one end (one end face) of the honeycomb structure 10, and the other end of the electrode layers 101a and 101b is the other end of the honeycomb structure 10. It means that it is in contact with (the other end face).

On the other hand, there is also a state in which at least one end of the electrode layers 101a and 101b in the "direction in which the cell 12 of the honeycomb structure 10 extends" is not in contact with (not reaching) the end (end face) of the honeycomb structure 10. This is a preferred embodiment. Thereby, the thermal impact resistance of the honeycomb structure can be improved.

In the honeycomb structure 10 of the present embodiment, for example, as shown in FIGS. 1 and 2, the electrode layers 101a and 101b have a planar rectangular member curved along the outer circumference of the cylindrical shape. Shape. Here, the shape when the curved electrode layers 101a and 101b are transformed into a non-curved flat member is referred to as the "planar shape" of the electrode layers 101a and 101b. The "planar shape" of the electrode layers 101a and 101b shown in FIGS. 1 to 3 is rectangular. Then, the term "outer peripheral shape of the electrode layer" means "outer peripheral shape in the planar shape of the electrode layer".

In the honeycomb structure 10 of the present embodiment, the outer peripheral shape of the strip-shaped electrode layer may be a shape in which rectangular corners are formed in a curved shape. With such a shape, the thermal impact resistance of the honeycomb structure can be improved. It is also preferable that the outer peripheral shape of the strip-shaped electrode layer is a shape in which the corners of the rectangle are chamfered in a straight line. With such a shape, the thermal impact resistance of the honeycomb structure can be improved.

In the honeycomb structure 10 of the present embodiment, the length of the current path is preferably 1.6 times or less the diameter of the honeycomb structure in the cross section orthogonal to the extending direction of the cell. If it exceeds 1.6 times, energy may be consumed unnecessarily. Here, the "current path" is a path through which a current flows. The "length of the current path" is 0.5 times the length of the "outer circumference" through which the current flows in the "cross section orthogonal to the extending direction of the cell" of the honeycomb structure. This means that it is the maximum length in the "current flow path" in the "cross section orthogonal to the cell extending direction" of the honeycomb structure. The "current path length" is a value measured along the unevenness or the surface inside the slit when the outer circumference is uneven or the honeycomb structure is formed with a slit that opens on the outer circumference. .. Therefore, for example, when the honeycomb structure is formed with a slit that opens on the outer periphery, the "current path length" is increased by approximately twice the depth of the slit.

The electrical resistivity of the electrode layers 101a and 101b is preferably 0.1 to 100 Ωcm, more preferably 0.1 to 50 Ωcm. By setting the electrical resistivity of the electrode layers 101a and 101b in such a range, the pair of electrode layers 101a and 101b effectively serve as electrodes in the pipe through which the high-temperature exhaust gas flows. If the electrical resistivity of the electrode layers 101a and 101b is smaller than 0.1 Ωcm, the temperature of the honeycomb portion near both ends of the electrode layers 101a and 101b may easily rise in the cross section orthogonal to the extending direction of the cell. If the electrical resistivity of the electrode layers 101a and 101b is larger than 100 Ωcm, it becomes difficult for current to flow, so that it may be difficult to play a role as an electrode. The electrical resistivity of the electrode layers 101a and 101b is a value at 400 ° C.

The electrode layers 101a and 101b preferably have a porosity of 30 to 60%, more preferably 30 to 55%. When the porosity of the electrode layers 101a and 101b is in such a range, a suitable electrical resistivity can be obtained. If the porosity of the electrode layers 101a and 101b is lower than 30%, the electrode layers 101a and 101b may be deformed during manufacturing. If the porosity of the electrode layers 101a and 101b is higher than 60%, the electrical resistivity may become too high. Porosity is a value measured with a mercury porosimeter.

The electrode layers 101a and 101b preferably have an average pore diameter of 5 to 45 μm, and more preferably 7 to 40 μm. When the average pore diameter of the electrode layers 101a and 101b is in such a range, a suitable electrical resistivity can be obtained. If the average pore diameter of the electrode layers 101a and 101b is smaller than 5 μm, the electrical resistivity may become too high. If the average pore diameter of the electrode layers 101a and 101b is larger than 45 μm, the strength of the electrode layers 101a and 101b may be weakened and the electrode layers 101a and 101b may be easily damaged. The average pore size is a value measured with a mercury porosimeter.

When the main component of the electrode layers 101a and 101b is a "silicon-silicon carbide composite material", the average particle size of the silicon carbide particles contained in the electrode layers 101a and 101b is preferably 10 to 60 μm, and is preferably 20 to 20 μm. It is more preferably 60 μm. When the average particle size of the silicon carbide particles contained in the electrode layers 101a and 101b is in such a range, the electrical resistivity of the electrode layers 101a and 101b can be controlled in the range of 0.1 to 100 Ωcm. If the average particle size of the silicon carbide particles contained in the electrode layers 101a and 101b is smaller than 10 μm, the electrical resistivity of the electrode layers 101a and 101b may become too large. If the average particle size of the silicon carbide particles contained in the electrode layers 101a and 101b is larger than 60 μm, the strength of the electrode layers 101a and 101b may be weakened and the silicon carbide particles may be easily damaged. The average particle size of the silicon carbide particles contained in the electrode layers 101a and 101b is a value measured by a laser diffraction method.

When the main component of the electrode layers 101a and 101b is "silicon-silicon carbide composite material", the electrode layers 101a and 101b have a relative "total mass of silicon carbide particles and silicon" contained in the electrode layers 101a and 101b. The ratio of the mass of silicon contained in 101b is preferably 20 to 40% by mass. The ratio of the mass of silicon to the "total mass of each of the silicon carbide particles and silicon" contained in the electrode layers 101a and 101b is more preferably 25 to 35% by mass. When the ratio of the mass of silicon to the "total mass of each of the silicon carbide particles and silicon" contained in the electrode layers 101a and 101b is in such a range, the electrical resistivity of the electrode layers 101a and 101b can be determined. It can be in the range of 0.1 to 100 Ωcm. If the ratio of the mass of silicon to the "total mass of each of the silicon carbide particles and silicon" contained in the electrode layers 101a and 101b is less than 20% by mass, the electrical resistivity may become too large. If it is larger than% by mass, it may be easily deformed during manufacturing.

(3. Metal electrode part)
As shown in FIG. 4, the honeycomb structure 10 comes into contact with the pair of metal electrode portions 1, 1 via the electrode layers 101a and 101b. Here, each of the metal electrode portions 1,1, a plate-like body portion 2, a plurality of tongues 3 projecting from the body portion (in the figure two) and a, a portion of the tongue 3 It contacts the honeycomb structure 10 (in the figure, it contacts the honeycomb structure 10 via the electrode layers 101a and 101b). As a result, the metal electrode portions 1 and 1 can be energized when a voltage is applied via the electrode layers 101a and 101b to generate heat in the honeycomb structure 10 by Joule heat. Therefore, the honeycomb structure 10 can be suitably used as a heater. The applied voltage is preferably 12 to 900 V, more preferably 64 to 600 V, but the applied voltage can be changed as appropriate.

FIG. 5 is a perspective view showing the metal electrode portion 1 according to the embodiment of the present invention. The metal electrode portion 1 includes a flat plate-shaped main body portion 2. A plurality of tongue pieces 3 are regularly arranged from the main body portion 2 upward in the drawing. Each tongue piece 3 includes a rising portion 3a from the main body portion 2 and a flat portion 3b protruding laterally from the rising portion 3a. Each tongue piece 3 is connected to the main body portion 2 by a piece 20 at the base thereof.

In this example, since the tongue piece 3 is formed by cutting the main body portion 2, a through hole 4 having substantially the same shape and size as the tongue piece 3 is formed. The flat portion 3b contacts the upper electrochemical cell.

FIG. 6 is a perspective view showing a metal electrode portion 1A according to another embodiment of the present invention. The metal electrode portion 1A includes a flat plate-shaped main body portion 2. A plurality of tongue pieces 13 are regularly arranged from the main body portion 2 upward in the drawing. Each tongue piece 13 includes a rising portion 13a from the main body portion 2, a flat portion 13b projecting laterally from the rising portion 13a, and a descending portion 13c extending from the flat portion 13b toward the through hole 4. There is. The flat portion 13b contacts the upper electrochemical cell. Each tongue piece 13 is connected to the main body portion 2 by a piece 20 at the base thereof.

FIG. 7 is a perspective view showing the metal electrode portion 1B according to still another embodiment of the present invention. The metal electrode portion 1B includes a flat plate-shaped main body portion 2. A plurality of tongue pieces 23 are regularly arranged from the main body portion 2 upward in the drawing. Each tongue piece 23 includes a rising portion 23a from the main body portion 2, a plurality of bent portions 23b, 23c, 23d, 23e and a flat portion 23f which are continuous thereto. The flat portion 23f contacts the upper electrochemical cell. Each tongue piece 23 is connected to the main body portion 2 by a piece 20 at the base thereof.

FIG. 8 is a perspective view showing the metal electrode portion 1C according to still another embodiment of the present invention. The metal electrode portion 1C includes a flat plate-shaped main body portion 2. A plurality of tongue pieces 33 are regularly arranged from the main body portion 2 upward in the drawing. Each tongue piece 33 includes a rising portion 33a from the main body portion 2, a curved portion 33b continuous with the curved portion 33b, and a flat portion 33c continuous with the curved portion 33b. The flat portion 33c contacts the upper electrochemical cell. Each tongue piece 33 is connected to the main body portion 2 by a piece 20 at the base thereof.

Further, the main body portion 2 is not particularly limited in shape as long as it has a plate shape, and may have a flat plate shape or a curved plate shape (see FIG. 4B). Further, when the main body portion 2 has a curved plate shape, it is preferable that the curved surface shape matches the side surface of the honeycomb structure 10. That is, it is preferable that the distance between the main body portion 2 and the honeycomb structure 10 is constant.

The planar shape of the tongue piece is not particularly limited. For example, as shown in FIGS. 9A and 9B, the tongue pieces 7A and 7B may be rectangular. Further, as shown in FIG. 9C, the tongue piece 7C may have an arc shape. As shown in FIG. 9D, the tongue piece 7D may have an oval shape.

Further, as shown in FIG. 10A, the tongue piece 7E may have a polygonal shape. Further, as shown in FIG. 10B, the tongue piece 7F may have a trapezoidal shape. Further, as shown in FIG. 10 (c), the tongue piece 7G may have a star shape. The tongue piece may exhibit various other irregular shapes.

The size of the tongue piece is not particularly limited. In order to increase the air permeability and the room for deformation, the height of the tongue piece is preferably 0.3 mm or more, more preferably 1.0 mm or more. On the other hand, if the tongue piece is too high, the gas utilization efficiency is lowered, so that the height of the tongue piece is preferably 5.0 mm or less. The height of the tongue piece is the maximum vertical distance from each part of the tongue piece to the main body part.

A part of the tongue piece 3 is in contact with the honeycomb structure 10 (see FIG. 4). When the electrode layer is provided on the surface of the honeycomb structure, a part of the tongue piece 3 comes into contact with the honeycomb structure 10 via the electrode layer. As a result, the metal electrode portion 1 and the honeycomb structure 10 are electrically connected. The contact between a part of the tongue piece 3 and the honeycomb structure 10 is not limited as long as the electrical connection between the metal electrode portion 1 and the honeycomb structure 10 can be secured. For example, the contact with the honeycomb structure 10 may be maintained by utilizing the elastic deformation of the tongue piece 3, and the tongue piece 3 is attached to the outer peripheral wall (or the electrode layer provided on the outer peripheral wall) of the honeycomb structure 10. It may be welded, and a fixed layer is formed by spraying a conductive metal material (for example, NiCr-based material or CoNiCr-based material) from above the tongue piece 3, and the tongue piece 3 is placed on the outer periphery of the honeycomb structure 10. It may be fixed to a wall (or an electrode layer provided on the outer peripheral wall). When the tongue piece 3 is fixed by forming the fixing layer, the "contact" between the part of the tongue piece 3 and the honeycomb structure 10 does not necessarily have to be a physical contact, and the tongue piece 3 and the honeycomb structure do not necessarily have to be in physical contact. Even if there is a space between the tongue piece 3 and the honeycomb structure 10, the metal electrode portion 1 and the honeycomb structure 10 are electrically connected by the conductive fixing layer, so that a part of the tongue piece 3 and the honeycomb structure 10 are connected to each other. You are in "contact". That is, in the present invention, "contact" refers not only to physical contact but also to electrical contact.

In this way, the metal electrode portion is formed into a plate-shaped main body portion and a plurality of tongue pieces protruding from the main body portion, and further, a part of the tongue pieces is configured to be in contact with the honeycomb structure to form the main body. Since the plurality of tongue pieces protruding from the portion can be independently deformed along the outer peripheral wall of the honeycomb structure, good electrical connection can be maintained even if the shape accuracy of the honeycomb structure is poor. Further, since each tongue piece is deformed separately, each tongue piece absorbs stress due to a difference in thermal expansion or the like, so that it is possible to prevent excessive stress from being applied to the contact point and the honeycomb structure.

Further, the shortest length A from the starting point of the tongue piece 3 protruding from the main body portion 2 to the portion where the tongue piece 3 most protrudes, and the direction orthogonal to the direction of protrusion from the main body portion 2 on the surface of the tongue piece 3. It is preferable that the minimum value B of the width satisfies the relationship of 1 ≦ A / B ≦ 10 (FIG. 11).

Here, the "location where the tongue piece protrudes most" means the location where the vertical distance L to the main body portion 2 is the longest (see FIGS. 11A and 11B). Further, "the shortest length A to the portion where the tongue piece protrudes most" means that the distance from the starting point where the tongue piece 3 protrudes from the main body portion 2 is the longest among the locations where the vertical distance to the main body portion 2 is the longest. The straight line distance to a short point (see FIGS. 11 (a) and 11 (b)). FIG. 11A shows a cross section in the thickness direction of the main body portion 2, A in the case where the tip of the tongue piece 3 has a flat plate shape parallel to the main body portion 2, and FIG. 11B shows a cross section in the thickness direction of the main body portion 2. , A is shown when the tip of the tongue piece 3 has a curved surface shape.

The "direction in which the tongue piece 3 protrudes from the main body portion 2" is orthogonal to the flow path direction of the cell 12 of the honeycomb structure along the surface of the tongue piece 3 from the starting point where the tongue piece 3 protrudes from the main body portion 2. The direction X is the direction X (see FIGS. 11C and 11D), and the “minimum value B of the width in the direction orthogonal to the direction protruding from the main body portion 2” is the direction X on the surface of the tongue piece 3. The width of the portion where the width of the tongue piece 3 is minimized in the vertical direction (see FIGS. 11C and 11D).

11 (c) is a top view of the metal electrode portion 1 of FIGS. 11 (a) and 11 (b), and FIG. 11 (d) is a top view of the tongue piece 3 of FIG. 11 (c) when it is extended in a plane. Is. In the illustrated embodiment, the tongue piece 3 has a neck portion and a head having a width wider than the width of the neck portion, and the width of the neck portion is constant, so that the width of the neck portion is B.

By setting A / B to 1 or more, the plurality of tongue pieces protruding from the main body portion can be easily deformed along the outer peripheral wall of the honeycomb structure, and the torsional stress applied to the tongue pieces can be relaxed. Further, by setting the A / B to 10 or less, the strength of the tongue piece can be maintained to a certain extent, fatigue fracture of the tongue piece can be prevented, and the width required for passing a large current can be secured. ..

Further, it is preferable that the length L1 of the neck of the tongue piece 3 and the length L2 of the head satisfy the relationship of 1 ≦ L1 / L2 ≦ 10 (see FIG. 11 (d)). By setting L1 / L2 to 1 or more, the plurality of tongue pieces protruding from the main body portion can be easily deformed along the outer peripheral wall of the honeycomb structure, and the torsional stress applied to the tongue pieces can be relaxed. Further, by setting L1 / L2 to 10 or less, the strength of the tongue piece can be maintained to a certain extent, fatigue fracture of the tongue piece can be prevented, and the width required for passing a large current can be secured. ..

The shapes of the neck and the head are not limited, and if the portion having a relatively narrow width and the portion having a relatively wide width can be visually distinguished, they can be referred to as a neck and a head, respectively.

Further, it is preferable that the tongue piece 3 has two or more bent portions (see FIG. 12). Since the tongue piece 3 has two or more bent portions, it is possible to improve the contact property with the honeycomb structure and adjust the stress applied to the honeycomb structure by utilizing the elastic deformation of the tongue piece 3.

The metal constituting the metal electrode portion 1 is not limited, but silver, copper, nickel, gold, palladium, silicon and the like are typical because of its availability. Preferably, the metal electrode portion 1 is an iron alloy, a nickel alloy, or a cobalt alloy. It is also possible to use carbon or ceramics instead of the metal electrode portion. Ceramics include, but are not limited to, ceramics containing at least one of Si, Cr, B, Fe, Co, Ni, Ti and Ta, for example silicon carbide, chromium silicate, boron carbide, chromium borate, Examples include siliceous tantalum. A composite material may be obtained by combining metal and ceramics.

Further, the metal electrode portion 1 preferably has a plurality of holes (see FIG. 11C). As a result, when the honeycomb structure generates heat, the heat insulating effect of the conductive connecting member itself is prevented, and the stress applied to the inside of the metal electrode portion 1 is relaxed by keeping the front and back temperatures of the metal electrode portion 1 constant, and the main body portion 2 Can be prevented from deforming. The plurality of holes may be through holes formed by cutting out a tongue piece from one metal plate, and a breathable material such as a mesh material, a plate material having vent holes, or an expanded metal is used as a main body portion. It may be a hole provided by the above.

Hereinafter, examples for better understanding the present invention and its advantages will be illustrated, but the present invention is not limited to the examples.

(Example)
A ceramic raw material was prepared by mixing silicon carbide (SiC) powder and metallic silicon (Si) powder in a mass ratio of 60:40. Then, hydroxypropyl methylcellulose as a binder and a water-absorbent resin as a pore-forming material were added to the ceramic raw material, and water was added to prepare a molding raw material. Then, the molding raw material was kneaded with a vacuum clay kneader to prepare a columnar clay. The binder content was 7 parts by mass when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder was 100 parts by mass. The content of the pore-forming material was 3 parts by mass when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder was 100 parts by mass. The water content was 42 parts by mass when the total of the silicon carbide (SiC) powder and the metallic silicon (Si) powder was 100 parts by mass. The average particle size of the silicon carbide powder was 20 μm, and the average particle size of the metallic silicon powder was 6 μm. The average particle size of the pore-forming material was 20 μm. The average particle size of the silicon carbide powder, the metallic silicon powder, and the pore-forming material refers to the arithmetic mean diameter based on the volume when the frequency distribution of the particle size is measured by the laser diffraction method.

The obtained columnar clay was molded using an extrusion molding machine to obtain a columnar honeycomb molded body having a square cross-sectional shape of each cell. The obtained honeycomb molded body was dried by high-frequency dielectric heating and then dried at 120 ° C. for 2 hours using a hot air dryer, and both bottom surfaces were cut by a predetermined amount to obtain a honeycomb dried body. The dried honeycomb body was degreased (temporarily fired) and then fired.

Next, hydroxypropyl methylcellulose as a binder, glycerin as a moisturizer, and a surfactant as a dispersant were added to the metallic silicon (Si) powder, and water was added and mixed. The mixture was kneaded to obtain an electrode layer forming raw material. This electrode layer forming raw material was applied to the side surface of the honeycomb fired body in a strip shape so as to have a thickness of 1.5 mm so as to extend between both end faces of the honeycomb fired body. The electrode layer forming raw material was applied to the side surface of the honeycomb fired body at two locations. Then, in the cross section orthogonal to the extending direction of the cell, one of the two portions coated with the electrode layer forming raw material is arranged so as to face the other with the center of the honeycomb fired body interposed therebetween. I made it.

Next, the electrode layer forming raw material applied to the honeycomb fired body was dried to obtain a honeycomb fired body with an unfired electrode. The drying temperature was 70 ° C.

Then, the honeycomb fired body with an unfired electrode was degreased (temporarily fired), fired, and further oxidized to obtain a honeycomb structure. The degreasing condition was 550 ° C. for 3 hours. The firing conditions were 1450 ° C. for 2 hours under an argon atmosphere. The conditions for the oxidation treatment were 1300 ° C. for 1 hour. The bottom surface of the obtained honeycomb structure was a circle having a diameter of 80 mm, and the length of the honeycomb structure in the extending direction of the cells was 75 mm.

Next, a metal electrode portion having a curved plate-shaped main body portion (stainless steel material) that matches the outer peripheral wall of the honeycomb structure and a tongue piece (stainless steel material) having the shape shown in FIG. 11 is formed on the outer periphery of the electrode layer of the honeycomb structure. The honeycomb structure was arranged on the surface so as to face each other with the center of the honeycomb structure interposed therebetween, and the tip of the honeycomb piece was fixed to the electrode layer by a welding method from above the tongue piece. Specific indicators of the tongue pieces of each Example and Comparative Example are shown in Table 1.

(Comparison example)
Preparations were made under the same conditions as in the examples except that the metal electrode portion was changed to a comb-shaped electrode having no tongue piece.

(Honeycomb breakage test)
A honeycomb structure in which a tongue piece (or comb-shaped electrode) is fixed by welding is wrapped with a ceramic mat and stored in a metal container, and a vibration test is performed in which vibration with a frequency of 100 Hz and an acceleration of 30 G is applied for 24 hours. The damaged state of the joint and honeycomb structure was visually confirmed. Table 1 shows the number of samples that could be visually confirmed.

(Discussion)
From the results shown in Table 1, it can be understood that in the examples of the present invention, damage to the joint portion / honeycomb structure is effectively suppressed as compared with the comparative examples. On the other hand, in the comparative example in which the metal electrode portion having no tongue piece was adopted, the stress relaxation was insufficient, and the joint portion and the honeycomb structure were frequently damaged.

10 ... Honeycomb structure 11 ... Partition wall 12 ... Cell 1, 1A, 1B, 1C ... Metal electrode part
7A, 7B, 7C, 7D, 7E, 7F, 7G ... Tongue pieces 101a, 101b ... Electrode layer 2 ... Body parts 3, 13, 23, 33 ... Tongue pieces 3a, 13a, 23a, 33a ... Rising parts 3b, 13b, 23f, 33c ... Flat part 20 ... One piece

Claims (7)

Honeycomb structure and
An electrically heated catalyst carrier including a pair of metal electrode portions arranged so as to face each other with the center of the honeycomb structure interposed therebetween.
One or both of the pair of metal electrode portions includes a plate-shaped main body portion and a plurality of tongue pieces protruding from the main body portion, and a part of the tongue pieces comes into contact with the honeycomb structure. A carrier for an electrically heated catalyst, which is characterized by being present. The shortest length A from the starting point of the tongue piece protruding from the main body portion to the most protruding portion of the tongue piece, and the width of the surface of the tongue piece in a direction orthogonal to the direction of protrusion from the main body portion. The carrier for an electrically heated catalyst according to claim 1, wherein the minimum value B satisfies the relationship of 1 ≦ A / B ≦ 10. The tongue piece has a neck and a head having a width wider than the width of the neck, and the length L1 of the neck and the length L2 of the head have a relationship of 1 ≦ L1 / L2 ≦ 10. The carrier for an electrically heated catalyst according to claim 1 or 2. The carrier for an electrically heated catalyst according to any one of claims 1 to 3, wherein the tongue piece has two or more bent portions. The electricity according to any one of claims 1 to 4, wherein the honeycomb structure is provided with a pair of electrode layers on its side surface, and the pair of electrode layers are arranged so as to face each other with the center of the honeycomb structure interposed therebetween. Carrier for heating type catalyst. The carrier for an electrically heated catalyst according to any one of claims 1 to 5, wherein the metal electrode portion is an iron alloy, a nickel alloy, or a cobalt alloy. The carrier for an electrically heated catalyst according to any one of claims 1 to 6, wherein the main body portion has a plurality of holes.

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